Abstract:

Maxillofacial prosthetics includes restoration of maxillary defects resulting from resection of palate and naso-sinus neoplasms with obturator prostheses, which may be colonised by microorganisms and function as a reservoir of infection. These patients commonly also require radiotherapy that can result in changes in oral flora and in saliva quality and quantity. The altered microflora, in individuals immunocompromised from cancer therapy, increases patient risk of prosthesis-related infections.

The aim of this study was to investigate microbial adhesion to, and colonisation of, maxillary obturator materials. The influence of saliva on adhesion of bacteria and yeasts to obturator materials was also investigated.

This study involved clinical and laboratory components. Clinically, microbial colonisation of obturator prostheses and adjacent tissues was investigated in patients referred for restoration of maxillary defects. This was undertaken at various stages of prosthodontic treatment by taking obturator and tissue swabs, saliva samples and reviewing tissue health. In the laboratory, RAPD PCR was used to identify bacteria and CHROMagar Candida was used to detect yeast species. DNA-DNA checkerboard analysis was also used for microbial detection. Microbial adhesion to obturator materials, and the influence of saliva on adhesion was investigated using static and flow adhesion assays. The analysis of salivary proteins affecting C. albicans adhesion to obturator materials was investigated using Western blot and blot overlay techniques. Identification of possible protein receptors for C. albicans adhesion to obturator materials was carried out by mass spectrometry analysis of the PAGE-separated protein bands.

Clinically, obturator prostheses and adjacent tissues in all patients investigated were colonised by Candida, with C. albicans identified in 14 out of 15 patients, at all stages of treatment. Microbial colonisation increased with the age of the prosthesis; the number of microorganisms colonising obturators only reduced following a reline or delivery of a new prosthesis. C. albicans colonisation increased significantly during radiotherapy. All patients with C. albicans colonisation greater than 1x105 colony forming units (cfu) per swab after one-week of radiotherapy subsequently required antifungal therapy and/or hospitalisation to manage oral complications during radiotherapy whereas those with C. albicans colonisation less than 1x104 cfu per swab after one-week didn’t require antifungal treatment. This suggests early obturator colonising levels may be a predictor for patient susceptibility to increased morbidity from head and neck radiotherapy. In the laboratory, Staphylococcus epidermidis and C. albicans were identified from swabs of obturators and tissues. S. epidermidis and C. albicans attached to all obturator materials and tended to attach more readily to surfaces with a greater surface roughness and surface energy. Saliva reduced adhesion of S. epidermidis to obturator materials compared with uncoated materials, in contrast, saliva promoted adhesion of C. albicans. Saliva from irradiated patients promoted more adhesion of both S. epidermidis and C. albicans than saliva from controls. Salivary proteins were selectively adsorbed to obturator materials and C. albicans bound to salivary proteins eluted from the same materials. The protein SPLUNC2 was shown, for the first time, to be associated with Candida adhesion to acrylic and may provide receptors for C. albicans adhesion to obturator materials.